Sign up to receive free email alerts when patent applications with chosen keywords are publishedSIGN UP

Abstract:

A semiconductor device includes a semiconductor substrate including a
bump electrode, a first insulating layer formed on the semiconductor
substrate and arranged to a lateral direction of the bump electrode, a
first wiring layer formed on the first insulating layer and connected to
the bump electrode, a second insulating layer formed on the first wiring
layer, a via hole formed in the second insulating layer, and reaching the
first wiring layer, a second wiring layer formed on the second insulating
layer and connected to the first wiring layer via a via conductor formed
in the via hole, and an external connection terminal connected to the
second wiring layer, wherein an elastic modulus of the second insulating
layer is set lower than an elastic modulus of the first insulating layer.

Claims:

1. A semiconductor device, comprising: a semiconductor substrate
including a bump electrode; a first insulating layer formed on the
semiconductor substrate, and arranged to a lateral direction of the bump
electrode; a first wiring layer formed on the first insulating layer, and
connected to the bump electrode; a second insulating layer formed on the
first wiring layer; a via hole formed in the second insulating layer, and
reaching the first wiring layer; a second wiring layer formed on the
second insulating layer, and connected to the first wiring layer via a
via conductor formed in the via hole; and an external connection terminal
connected to the second wiring layer; wherein an elastic modulus of the
second insulating layer is set lower than an elastic modulus of the first
insulating layer.

2. A semiconductor device according to claim 1, wherein the second wiring
layer is formed to extend outward from an outer periphery of the via
hole, and the via conductor is formed of a conductive paste or a solder.

3. A semiconductor device according to claim 2, wherein the via conductor
is filled in the via hole, and is formed to cover the second wiring layer
located in vicinity of the via hole.

4. A semiconductor device according to claim 2, wherein the second wiring
layer is formed of a copper foil.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based upon and claims the benefit of priority
of the prior Japanese Patent Application No. 2010-140940, filed on Jun.
21, 2010, the entire contents of which are incorporated herein by
reference.

FIELD

[0002] It is related to a semiconductor device.

BACKGROUND

[0003] Recently, with the high performance of the multimedia equipment,
etc., the high density in the mounting technology serving as the
interface between LSI and the electronic equipment is proceeding.

[0004] As the IC package responding to such request, there is the CSP
(Chip Size Package) which is packaged in substantially equal size to the
chip size. Further, the wafer level CSP from which individual CSPs are
obtained by applying the film formation, the processing, etc. associated
with the CSP structure in a wafer level, and then dicing such wafer, is
known.

[0005] In the wafer level CSP, the rewiring is formed to be connected to
the connection pads of the silicon wafer in which the transistors are
formed, and then the bump electrodes are formed on the rewiring.

[0006] In Patent Literature 1 (Japanese Patent No. 4121542) and Patent
Literature 2 (Japanese Patent No. 4431628), it is set forth that an
insulating layer is formed on a semiconductor substrate having bump
electrodes such that upper parts of the bump electrodes are exposed, and
then wiring patterns connected to the bump electrodes are formed.

[0007] In Patent Literature 3 (Japanese Laid-Open Patent Publication No.
2002-43753), it is set forth that an insulating resin layer and a copper
foil are laminated on the inner layer wiring plate, then openings are
formed in the copper foil, then non-penetration holes are formed in the
insulating resin layer through the opening in the copper foil by the
blasting process, and then conductor circuit patterns are formed in the
non-penetration holes by the plating.

[0008] In the semiconductor device having the CSP structure in the prior
art, in most cases the rewiring formed on the silicon wafer is formed as
a single layer, and therefore employment of the multilayer wiring
structure is not considered at all (for example, Patent Literatures 1 and
2). In particular, in the semiconductor devices such as ASI, Logic, etc.,
it is required that the rewiring having the multilayer structure should
be formed in order to correspond to the multi-pin type.

[0009] Further, in the prior art, the reliability in mounting the
semiconductor device onto the mounting substrate is not considered.
Therefore, such a problem exists that the conduction failure is caused
due to the fact that a stress is concentrated in the external connection
terminals of the semiconductor device at a time of mounting.

SUMMARY

[0010] According to one aspect discussed herein, there is provided a
semiconductor device includes a semiconductor substrate including a bump
electrode, a first insulating layer formed on the semiconductor
substrate, and arranged to a lateral direction of the bump electrode, a
first wiring layer formed on the first insulating layer, and connected to
the bump electrode, a second insulating layer formed on the first wiring
layer, a via hole formed in the second insulating layer, and reaching the
first wiring layer, a second wiring layer formed on the second insulating
layer, and connected to the first wiring layer via a via conductor formed
in the via hole, and an external connection terminal connected to the
second wiring layer, wherein an elastic modulus of the second insulating
layer is set lower than an elastic modulus of the first insulating layer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. 1 is a sectional view and plan view (#1) depicting a method of
manufacturing a semiconductor device according to an embodiment;

[0012] FIGS. 2A and 2B are sectional views (#2) depicting the method of
manufacturing the semiconductor device according to the embodiment;

[0013] FIGS. 3A and 3B are sectional views (#3) depicting the method of
manufacturing the semiconductor device according to the embodiment;

[0014] FIGS. 4A and 4B are sectional views (#4) depicting the method of
manufacturing the semiconductor device according to the embodiment;

[0015] FIGS. 5A and 5B are sectional views (#5) depicting the method of
manufacturing the semiconductor device according to the embodiment;

[0016] FIGS. 6A and 6B are sectional views (#6) depicting the method of
manufacturing the semiconductor device according to the embodiment;

[0017] FIGS. 7A and 7B are sectional views (#7) depicting the method of
manufacturing the semiconductor device according to the embodiment;

[0018] FIGS. 8A and 8B are sectional views (#8) depicting the method of
manufacturing the semiconductor device according to the embodiment;

[0019] FIGS. 9A and 9B are sectional views (#9) depicting the method of
manufacturing the semiconductor device according to the embodiment;

[0020]FIG. 10 is a sectional view (#10) depicting the method of
manufacturing the semiconductor device according to the embodiment;

[0021] FIGS. 11A and 11B are sectional views (#11) depicting the method of
manufacturing the semiconductor device according to the embodiment;

[0022]FIG. 12 is a sectional view (#12) depicting the method of
manufacturing the semiconductor device according to the embodiment;

[0023]FIG. 13 is a sectional view (#13) depicting the method of
manufacturing the semiconductor device according to the embodiment;

[0024]FIG. 14 is a sectional view depicting a semiconductor device
according to the embodiment; and

[0025] FIG. 15 is a sectional view depicting a state that the
semiconductor device according to the embodiment is mounted on a mounting
substrate.

DESCRIPTION OF EMBODIMENT

[0026] An embodiment of the present invention will be explained with
reference to the accompanying drawings hereinafter.

[0027] FIG. 1 to FIG. 13 are sectional views depicting a method of
manufacturing a semiconductor device according to an embodiment, and FIG.
14 is a sectional view depicting a semiconductor device according to the
embodiment.

[0028] In the method of manufacturing the semiconductor device according
to the embodiment, first, a silicon wafer 10 as depicted in FIG. 1 is
prepared. In the present embodiment, the silicon wafer 10 is illustrated
as a semiconductor wafer.

[0029] The silicon wafer 10 includes connection pads 12 and a passivation
layer 14 (protection insulating layer) in which opening portions 14x
which expose the connection pads 12 are provided, to the uppermost part
thereof.

[0030] The connection pad 12 is formed of aluminum, aluminum alloy, or the
like, and the passivation layer 14 is constructed by forming a silicon
nitride layer 14a and a polyimide resin layer 14b sequentially from the
bottom. In this case, the passivation layer 14 may be formed of the
silicon nitride layer 14a by omitting the polyimide resin layer 14b.

[0031] A plurality of element forming areas T in each of which circuit
elements such as transistor (semiconductor element), capacitor, resistor,
and the like are formed are provided in the silicon wafer 10. A
multilayer wiring (not shown) for connecting various circuit elements is
formed on each element forming area T, and the multilayer wiring is
connected to the connection pads 12.

[0032] To explain further by reference to a plan view of FIG. 1, a large
number of chip areas A each of which contains the element forming area T
are provided in the silicon wafer 10. The chip area A is surrounded by
dicing lines D which are arranged in a grid-like fashion, and is defined.

[0033] In the example in the plan view of FIG. 1, the connection pads 12
are arranged as the area-array type, and are arranged in a grid-like
fashion in the whole area of each chip area A. Otherwise, the connection
pads 12 may be arranged as the peripheral type, and may be arranged on
the peripheral part of each chip area A respectively. The silicon wafer
10 becomes individual semiconductor chips (semiconductor devices) by
dicing the silicon wafer 10 along the dicing lines D so as to obtain
respective chip areas A.

[0034] In following steps, while partially referring to one chip area A of
the silicon wafer 10 in FIG. 1, explanation will be made hereunder.

[0035] As depicted in FIG. 2A, the silicon wafer 10 explained in FIG. 1 is
prepared. A thickness of the silicon wafer 10 is about 600 to 800 μm.

[0036] Then, as depicted in FIG. 2B, a dry film resist 16 of about 50
μm thickness is pasted onto the silicon wafer 10, and then is
exposed/developed based on the photolithography, and thus the dry film
resist 16 is patterned. Accordingly, the dry film resist 16 is left on
each chip area A, and an opening portion 16a of the dry film resist 16 is
arranged on the dicing lines D.

[0037] Then, as depicted in FIG. 3A, while using the dry film resist 16 as
a mask, the passivation layer 14 is etched from its upper surface to the
thickness direction through the opening portions 16a of the dry film
resist 16 by the wet blasting method. Accordingly, a concave portion C is
formed in the dicing lines D (FIG. 1) of the silicon wafer 10
respectively. The concave portions C are formed in a grid-like fashion so
as to surround each chip area A.

[0038] As described later, the concave portions C formed in the silicon
wafer 10 acts as an anchor that increases the adhesion of an interlayer
insulating layer formed on the silicon wafer 10.

[0039] Then, as depicted in FIG. 3B, the dry film resist 16 is removed by
a resist stripper. In this case, the similar mask may be formed by using
a liquid resist instead of the dry film resist 16.

[0040] Then, as depicted in FIG. 4A, the cleaning process is applied to
the upper surface side of a resultant structure depicted in FIG. 3B by an
oxygen plasma. Accordingly, a surface of the passivation layer 14 is
reformed (roughened), and also surfaces of the connection pads 12 are
cleaned.

[0041] Then, as depicted in FIG. 4B, a gold (Au) wire bump 18 whose top
end is sharpened is formed on the connection pads 12 respectively on the
basis of the wire bonding method. The gold wire bump 18 is illustrated as
the bump electrode, but copper (Cu) wire bumps having the similar shape
may be formed on the basis of the wire bonding method.

[0042] Otherwise, a gold (Au) bump, or the like may be formed by the
electroplating method, or a nickel (Ni) bump/a gold (Au) bump may be
formed sequentially by the electroless plating method.

[0043] Then, as depicted in FIG. 5A, a resin film 20a kept in a B-stage
(semi-cured state) is pasted onto the silicon wafer 10 on which the gold
wire bumps 18 are provided. As the resin film 20a, a thermosetting resin
such as an epoxy resin, a polyimide resins, or the like is used.

[0044] A thickness of the resin film 20a is set to a thickness (e.g., 30
μm) which is slightly thinner than a height of the gold wire bump 18.
Thus, such a situation is obtained that the top end of the gold wire bump
18 is exposed from an upper surface of the resin film 20a.

[0045] Then, as depicted in FIG. 5B, the resin film 20a is pressed
downward by a pressing jig (not shown) and is planarized, and then a heat
treatment is applied to the resin film 20a at a temperature of about
180° C. Thus, the resin film 20a kept in a B-stage is cured, and a
first interlayer insulating layer 20 is obtained.

[0046] At this time, the top ends of the gold wire bumps 18 are crushed by
the planarizing process, and thus connection portions 18a are obtained.
In this manner, the connection portions 18a of the gold wire bumps 18 and
an upper surface of the first interlayer insulating layer 20 are
planarized so as to constitute the identical surface.

[0047] Also, as described above, the concave portion C is formed on the
dicing lines D (FIG. 1) on the silicon wafer 10 respectively. Therefore,
the first interlayer insulating layer 20 is formed on the silicon wafer
10 with good adhesion by the anchor effect.

[0048] Here, an elastic modulus of the first interlayer insulating layer
20 formed to the lateral direction of the gold wire bump 18 is set to 3
to 20 GPa. Thus, the first interlayer insulating layer 20 is set to a
film quality whose strain is relatively small to a stress. The first
interlayer insulating layer 20 has an adequate mechanical strength, and
the gold wire bumps 18, etc. are protected with the first interlayer
insulating layer 20.

[0049] As described later, an elastic modulus of a second interlayer
insulating layer, which is formed on the first interlayer insulating
layer 20 and is arranged just under the external connection terminals
(solder balls, or the like), is set lower than an elastic modulus of the
first interlayer insulating layer 20 in order to absorb a stress applied
to the external connection terminals. Thus, the second interlayer
insulating layer is set to a relatively soft film quality.

[0050] An elastic modulus of the first interlayer insulating layer 20 can
be adjusted by a content of inorganic fillers, e.g., silica, or the like,
contained in a resin. In order to obtain the first interlayer insulating
layer 20 whose elastic modulus is 3 to 20 GPa, a content of inorganic
fillers is set to 40% to 90%.

[0051] Then, as depicted in FIG. 6A, the asking process is applied to the
first interlayer insulating layer 20 and the connection portions 18a of
the gold wire bumps 18 by an oxygen (O2) plasma into which carbon
tetrafluoride (CF4) is added.

[0052] Accordingly, the resin remaining in the connection portions 18a of
the gold wire bumps 18 is removed, and the connection portions 18a can be
exposed in a clean condition. At the same time, the surface of the first
interlayer insulating layer 20 is also lightly etched and roughened, and
thus the anchor is formed on the surface.

[0053] Then, as depicted in FIG. 6B, a metal layer is formed on the first
interlayer insulating layer 20 by the sputter method (PVD method), and
thus a seed layer 30a is obtained. Since the surface of the first
interlayer insulating layer 20 is roughened, the seed layer 30a is formed
on the first interlayer insulating layer 20 with good adhesion.

[0054] As a preferable example of the seed layer 30a, a laminated film
which is obtained by forming a titanium (Ti) layer (thickness: 0.1 μm
or more)/a copper (Cu) layer (thickness: 0.2 to 0.5 μm) sequentially
from the bottom is used. Otherwise, as the seed layer 30a, a laminated
film which is obtained by forming a chromium (Cr) layer (thickness: 0.035
μm or more)/a copper (Cu) layer (thickness: 0.2 to 0.5 μm)
sequentially from the bottom is used.

[0055] Then, as depicted in FIG. 7A, a plating resist 19 in which opening
portions 19a are provided on the parts where the first wiring layer is
arranged is formed on the seed layer 30a on the basis of the
photolithography. Then, a metal pattern layer 30b is formed in the
opening portions 19a of the plating resist 19 respectively by the
electroplating that utilizes the seed layer 30a as a plating power
feeding path. The metal pattern layer 30b is formed of the wiring
material such as copper, or the like.

[0056] Then, the plating resist 19 is removed, and then the seed layer 30a
is etched while using the metal pattern layer 30b as a mask.

[0057] Accordingly, as depicted in FIG. 7B, first wiring layers 30 each
constructed by the seed layer 30a and the metal pattern layer 30b are
obtained. The first wiring layer 30 is formed to be connected
electrically to the connection portion 18a of the gold wire bump 18.
Then, the anchor is formed by roughening the surface of the first wiring
layer 30 by means of a chemical solution in a formic acid series.

[0058] Then, as depicted in FIG. 8A, a resin film with copper foil CF
having such a structure that a copper foil 32a is pasted onto a resin
film 22a kept in a B-stage (semi-cured state) is prepared. A thickness of
the copper foil 32a is 5 to 18 μm, and a thickness of the resin film
22a is preferably 30 to 60 μm. As the resin film 22a, a thermosetting
resin such as an epoxy resin, a polyimide resin, or the like is used.

[0059] Then, a surface of the resin film 22a of the resin film with copper
foil CF is pressure-bonded to the first wiring layers 30. Then, the resin
film 22a kept in a B-stage is cured by applying a heat treatment at a
temperature of about 180° C., and a second interlayer insulating
layer 22 is obtained.

[0060] Since the surface of the first wiring layers 30 is roughened, the
second interlayer insulating layer 22 is formed on the first wiring
layers 30 with good adhesion.

[0061] Here, an elastic modulus of the second interlayer insulating layer
22 is set to 0.5 to 2 GPa, and the second interlayer insulating layer 22
is set to a soft film quality whose strain is relatively large to a
stress. That is, an elastic modulus of the second interlayer insulating
layer 22 is set lower than an elastic modulus of the first interlayer
insulating layer 20. As described later, this is because it causes the
second interlayer insulating layer 22 to absorb the stress applied to the
external connection terminals which are mounted just over the second
interlayer insulating layer 22.

[0062] An elastic modulus of the second interlayer insulating layer 22 can
be adjusted by a content of inorganic fillers, e.g., silica, or the like,
contained in a resin. In order to obtain the second interlayer insulating
layer 22 whose elastic modulus is 0.5 to 2 GPa, a content of inorganic
fillers is set to 0% to 20%. Otherwise, an elastic modulus may be
adjusted by employing a resin whose skeleton is different mutually
between the first interlayer insulating layer 20 and the second
interlayer insulating layer 22.

[0063] Respective thicknesses of the first interlayer insulating layer 20
and the second interlayer insulating layer 22 can be set arbitrarily. In
this case, it is preferable that, from the viewpoint that it cases the
insulating layer to absorb sufficiently the stress applied to the
external connection terminals, a thickness of the second interlayer
insulating layer 22 whose elastic modulus is low should be set relatively
thicker. As a preferable example, the second interlayer insulating layer
22 is set to have about one to two times the thickness of the first
interlayer insulating layer 20. For example, in case a thickness of the
first interlayer insulating layer 20 is 30 μm, a thickness of the
second interlayer insulating layer 22 is set to 30 to 60 μm.

[0064] In the present embodiment, the resin film with copper foil CF is
pasted onto the first wiring layers 30. In this case, various laminated
films in each of which a metal layer is laminated on an insulating layer
can be used.

[0065] Then, as depicted in FIG. 8B, a dry film resist 23 in which opening
portions 23a are provided on parts corresponding to the connection
portions of the first wiring layers 30 is formed. Then, the copper foil
32a is wet-etched through the opening portions 23a of the dry film resist
23 by a copper etchant such as a copper (II) chloride aqueous solution,
or the like while using the dry film resist 23 as a mask, and thus
opening portions 32x are formed in the copper foil 32a.

[0066] Then, as depicted in FIG. 9A, the second interlayer insulating
layer 22 exposed from the opening portions 32x of the copper foil 32a is
etched by the wet blasting method in a state that the dry film resist 23
is still left (FIG. 8B). Thus, via holes VH each reaching the connection
portion of the first wiring layer 30 are formed. A diameter of the via
hole VH is set to 50 to 80 μm, for example. At this time, the dry film
resist 23 (FIG. 8B) is etched simultaneously by the wet blasting method,
and is removed.

[0067] The wet blasting method indicates such a processing method that the
slurry which is obtained by mixing grains such as alumina abrasive
grains, or the like and a liquid such as water, or the like is sprayed at
a high speed from a spray nozzle by using a force of compressed air, so
that the work piece is etched physically by the grains contained in the
slurry.

[0068] Also, in the wet blasting method, an etching rate of the first
wiring layer 30 (copper) is considerably low. Therefore, the first wiring
layer 30 acts as a stopper upon etching the second interlayer insulating
layer 22.

[0069] Also, a thickness of the dry film resist 23 (FIG. 8B) is set such
that the dry film resist 23 completely disappears at the halfway time in
etching of the second interlayer insulating layer 22. After the dry film
resist 23 disappeared, the copper foil 32a functions as a mask.

[0070] Accordingly, the surface of the copper foil 32a serving as the
second wiring layer later is roughened by the wet blasting method, and
the anchor is simultaneously formed.

[0071] Also, unlike the present embodiment, in the case that the via holes
VH are formed in the second interlayer insulating layer 22 by the laser,
a resin smear is produced in the via holes VH. Therefore, the desmear
process must be executed by the wet process such as the permanganic acid
method, or the like.

[0072] However, in the case that the wet blasting method is used, a resin
smear is hardly produced. Thus, the clean via holes VH can be obtained
easily by the water rinsing after the via holes VH are formed in the
second interlayer insulating layer 22. In this manner, in the present
embodiment, the desmear process that affects the loads to the environment
can be omitted.

[0073] Then, as depicted in FIG. 9B, an etching resist (not shown) is
patterned on the copper foil 32a, and then the copper foil 32a is etched
by using the etching resist as a mask. Thus, second wiring layers 32 are
obtained.

[0074] At this point of time, a via conductor is not formed in the via
holes VH respectively. Hence, the first wiring layer 30 and the second
wiring layer 32 are in a state that these layers are not electrically
connected.

[0075] Therefore, a via conductor is formed in the via hole VH such that
the first wiring layer 30 and the second wiring layer 32 are electrically
connected via the via conductor.

[0076] In the present embodiment, as the method of forming the via
conductor, the approach such as the sputter method, the electroplating
method, the electroless plating method, or the like, which brings about
an increase in cost, is not employed.

[0077] More particularly, as depicted in FIG. 10, a conductive paste 40
such as a silver paste, or the like is coated to the inside of the via
hole VH from a nozzle 5 of a dispenser equipment (not shown) by the
dispensing method, and then the conductive paste 40 is subjected to a
heat treatment and is cured. Thus, the first wiring layer 30 and the
second wiring layer 32 are electrically connected. The conductive paste
40 is obtained by dispersing conductive particles such as silver grains,
or the like into the thermosetting resin as the binder.

[0078] As depicted in FIG. 11A, in the case that the conductive paste 40
is formed by the dispensing method, such conductive paste 40 is filled in
the via hole VH and is formed to cover the second wiring layer 32 located
in vicinity of the via hole VH.

[0079] Otherwise, the conductive paste 40 may be formed in the via hole VH
by the ink jetting method instead of the dispensing method. As depicted
in FIG. 11B, in the case that the ink jetting method is used, the
conductive paste 40 is not embedded in the via hole VH, and a concave
portion is left in the via hole VH.

[0080] That is, the conductive paste 40 is formed along the bottom surface
and the side surface of the via hole VH as the so-called conformal via.
Also in the case that the ink jetting method is used, the conductive
paste 40 is formed to cover the second wiring layer 32 located in
vicinity of the via hole VH.

[0081] Also, as other method of forming the via conductor, a
photosensitive conductive paste containing a photosensitizing agent may
be used. In this case, the photosensitive conductive paste is coated on
the whole upper surface of a silicon wafer 10 by the spin coater, or the
like, and then is exposed/developed on the basis of the photolithography.
Thus, the conductive paste 40 is formed selectively in the via hole VH so
that the first wiring layer 30 and the second wiring layer 32 are
electrically connected. As the photosensitive conductive paste, there are
a photosensitive silver paste, and the like. In the case that the
photosensitive conductive paste is used, the conductive paste 40 is
formed as the conformal via like the case where the conductive paste 40
is formed by the ink jetting method.

[0082] Otherwise, besides the conductive paste 40, the solder may be
filled in the via hole VH, and the first wiring layer 30 and the second
wiring layer 32 may be electrically connected via the solder. In this
case, a solder ball is mounted in the via hole VH, and the solder is
filled in the via hole VH by the reflow heating. Alternatively, a solder
paste (cream solder) may be coated selectively to the via hole VH.

[0083] According to the above approach, without the use of either the
sputter method that brings about an increase in cost or the plating
method that affects the heavy loads to the environment and needs the
complicated steps, the via conductor can be formed easily at a low cost
by forming the conductive paste or the solder in the via hole VH.

[0084] In this manner, the interlayer connecting structure in which the
second wiring layer 32 is connected to the first wiring layer 30 via the
via hole VH formed in the second interlayer insulating layer 22 is
obtained. Thus, the rewiring (the first and second wiring layers 30, 32)
having the multilayer structure is connected to the gold wire bump 18
which is provided to the silicon wafer 10. A pitch of the connection pads
12 of the silicon wafer 10 is pitch-converted by the rewiring (the first
and second wiring layers 30, 32) so as to correspond to a pitch of the
connection electrodes of the mounting substrate.

[0085] Here, the step of forming the second wiring layers 32 by patterning
the copper foil 32a is executed after the via holes VH are formed by the
wet blasting method. But this step may be executed after the conductive
paste 40 is formed in the via holes VH (after FIGS. 11A and 11B).

[0086] After this, as depicted in FIG. 12, a solder resist 24 in which an
opening portion 24a is provided on the connection portions of the second
wiring layers 32 respectively is formed. Since the surfaces of the second
wiring layers 32 are roughened, the solder resist 24 is formed on the
second wiring layers 32 with good adhesion. Then, the ashing process is
applied to the surface of the solder resist 24 by using an oxygen plasma,
so that the surface of the solder resist 24 is reformed to hydrophilicity
and thus a wettability is improved.

[0087] Then, as depicted in FIG. 13, the solder ball is mounted on the
opening portion 24a of the solder resist 24, and then the reflow heating
is applied. Thus, an external connection terminal 34 connected to the
connection portion of the second wiring layer 32 is formed. As the solder
ball, a ball which is constructed by forming a solder layer on an outer
surface of a resin ball may be used.

[0088] Subsequently, as also depicted in FIG. 13, as the need arises, a
thickness of the silicon wafer 10 may be reduced up to about 50 to 300
μm by grinding the back surface of the silicon wafer 10 by means of
the grinder. Then, the silicon wafer 10 is cut along the dicing lines D
(FIG. 1). Accordingly, as depicted in FIG. 14, the silicon wafer 10 is
divided into individual pieces as silicon substrates 10a (semiconductor
substrates), thus an individual semiconductor device 1 including a CSP
structure is obtained.

[0089] Here, in the present embodiment, the two-layered multilayer wiring
(the first and second wiring layers 30, 32) is illustrated. In this case,
the multilayer wiring can be formed in any number of lamination layers by
repeating the above steps in FIG. 8A to FIGS. 11A and 11B.

[0090] As explained above, in the method of manufacturing the
semiconductor device of the present embodiment, first, the gold wire bump
18 is formed on the connection pads 12 of the silicon wafer 10 in which
the circuit elements are formed respectively, and then the first
interlayer insulating layer 20 is formed such that the connection
portions 18a as the top parts of the gold wire bumps 18 are exposed.

[0091] Then, the first wiring layer 30 connected to the gold wire bumps 18
is formed on the first interlayer insulating layer 20. Then, the resin
film with copper foil CF is pressure-bonded to the first wiring layers
30, and the resin film 22a is utilized as the second interlayer
insulating layer 22. An elastic modulus of the second interlayer
insulating layer 22 is set lower than that of the first interlayer
insulating layer 20, and the second interlayer insulating layer 22
functions as a stress absorbing layer which absorbs a stress applied to
the external connection terminals 34.

[0092] Then, the dry film resist 23 in which the opening portion 23a are
provided in the parts corresponding to the connection portions of the
first wiring layers 30 is formed on the copper foil 32a. Then, the
opening portions 32x are formed by etching the copper foil 32a.

[0093] Then, in this state, the second interlayer insulating layer 22 is
etched through the opening portions 32x of the copper foil 32a by the wet
blasting method, and thus the via holes VH each reaching the first wiring
layer 30 are formed.

[0094] Then, the first wiring layer 30 and the copper foil 32a are
electrically connected by forming the via conductor made of the
conductive paste 40 or the solder in the via holes VH respectively. The
copper foil 32a is patterned in a predetermined stage, and becomes the
second wiring layers 32. Then, the external connection terminal 34 is
provided onto the second wiring layers 32 respectively.

[0095] By using of such method, there is no need to use the following
technologies when the second wiring layers 32 each connected to the first
wiring layer 30 via the via hole VH are formed. That is, there is no need
to use the technologies of 1) formation of the photo via using a
photosensitive polyimide, 2) film formation of the metal layer (the seed
layer, or the like) by the sputter method, 3) formation of the via hole
by the laser, 4) desmear process applied to the via hole by a strong
alkaline liquid in a permanganic acid series, and 5) formation of wiring
by the wet plating (electroless Cu plating/electrolytic Cu plating).

[0096] Accordingly, the number of steps needed for the manufacture can be
greatly reduced, and thus a manufacturing cost can be reduced. Also, the
desmear process or the wet plating process is not needed. Therefore, a
harmful waste liquid can be reduced, and reduction of the loads affected
to the environment can be achieved.

[0097] In this manner, in the present embodiment, the rewiring (the first
and second wiring layers 30, 32) having the multilayer structure
including the second interlayer insulating layer 22 which absorbs a
stress applied to the external connection terminals can be formed on the
silicon wafer 10 by the simple method that can attain a cost reduction.
Accordingly, the present embodiment can deal easily with the manufacture
of the semiconductor device such as ASIC, Logic, or the like, that the
multi-pin type is required.

[0098] As depicted in FIG. 14, in the semiconductor device 1 of the
present embodiment, the element forming areas T (FIG. 1) in which the
circuit elements such as the transistor, etc. are formed are provided in
the silicon substrate 10a (semiconductor substrate). The connection pads
12 are provided on the silicon substrate 10a, and the connection pads are
connected to the element forming areas T (FIG. 1) via the multilayer
wiring (not shown).

[0099] The gold wire bump 18 is formed on the connection pads 12
respectively, and the first interlayer insulating layer 20 is formed to
the lateral direction of the gold wire bumps 18. The connection portions
18a of the gold wire bumps 18 are arranged at the identical height with
the upper surface of the first interlayer insulating layer 20, and they
are planarized.

[0100] Also, the first wiring layers 30 each connected to the connection
portion 18a of the gold wire bump 18 are formed on the first interlayer
insulating layer 20. The second interlayer insulating layer 22 is formed
on the first wiring layers 30, and the via holes VH each reaching the
connection portion of the first wiring layer 30 is formed in the second
interlayer insulating layer 22.

[0101] The second wiring layer 32 which extends outward from the outer
periphery of the via hole VH is formed on the second interlayer
insulating layer 22. The second wiring layer 32 is formed by patterning
the copper foil 32a.

[0102] Further, the conductive paste 40 is filled in the via holes VH
respectively. The conductive paste 40 is formed from the inside of the
via hole VH to its outer vicinity area, and is formed to cover the second
wiring layer 32 located in vicinity of the via hole VH.

[0103] According to this, the first wiring layer 30 is connected
electrically to the second wiring layer 32 via the conductive paste 40
(via conductor). The first wiring layer 30 and the second wiring layer 32
may be connected by using the solder instead of the conductive paste 40.

[0104] As described above, there is no necessity that the conductive paste
40 should always be formed to embed the via hole VH, and the conductive
paste 40 may be formed along the bottom surface and the side surface of
the via hole VH as the conformal via.

[0105] The semiconductor device 1 of the present embodiment is
manufactured by the above-mentioned manufacturing method. As a
consequence, the semiconductor device 1 has such a structure that the
second wiring layer 32 is not arranged on the conductive paste 40 (via
conductor) in the via hole VH.

[0106] Also, the solder resist 24 in which the opening portion 24a is
provided on the connection portions of the second wiring layers 32
respectively is formed. Then, the external connection terminal 34
connected to the second wiring layer 32 is provided on the opening
portions 24a of the solder resist 24 respectively.

[0107] A pitch of the connection pads 12 of the silicon substrate 10a is
pitch-converted by the rewiring (the first and second wiring layers 30,
32) so as to correspond to a pitch of the connection electrodes of the
mounting substrate.

[0108] An elastic modulus of the second interlayer insulating layer 22 is
set lower than that of the first interlayer insulating layer 20. Thus, a
stress applied to the external connection terminals can be absorbed by
the second interlayer insulating layer 22.

[0109] As depicted in FIG. 15, the external connection terminals 34 of the
semiconductor device 1 are connected to connection electrodes 52 of a
mounting substrate 50 (mother board, or the like) by the reflow
soldering, or the like. Then, an underfill resin 54 is filled into a
clearance located under the semiconductor device 1. There is no need that
the underfill resin 54 should always be filled, and in some cases the
underfill resin 54 may be omitted.

[0110] When the semiconductor device 1 is mounted on the mounting
substrate, a thermal stress is caused due to a difference of a
coefficient of thermal expansion between the semiconductor device 1 and
the mounting substrate at a time of heating process, or the like, and a
stress is readily concentrated in the external connection terminals 34 of
the semiconductor device 1. As a result, in some cases the conduction
failure may be caused because either the cracks are generated around the
external connection terminals 34 of the semiconductor device 1 or the
boundary separations are generated.

[0111] In the present embodiment, the second interlayer insulating layer
22 whose elastic modulus is set lower than that of the first interlayer
insulating layer 20 and which is set to soft film quality is present just
under (in FIG. 15, just over) the external connection terminals 34 of the
semiconductor device 1. Accordingly, the second interlayer insulating
layer 22 functions as the stress absorbing layer for absorbing the stress
which is concentrated in the external connection terminals 34.

[0112] Accordingly, the stress concentration to the external connection
terminals 34 of the semiconductor device 1 is eased. As a result, such a
drawback can be solved that either the cracks are generated around the
external connection terminals 34 of the semiconductor device 1 or the
boundary separations are generated.

[0113] Also, the first interlayer insulating layer 20 whose elastic
modulus is higher than that of the second interlayer insulating layer 22
to have an adequate hardness is present just under (in FIG. 15, right
over) the second interlayer insulating layer 22. Therefore, the thin type
semiconductor device 1 having enough mechanical strength is constructed.

[0114] As a result, the highly reliable electrical connection can be
obtained between the semiconductor device 1 and the mounting substrate
50, and the highly reliable electronic module can be constructed.

[0115] In the above present embodiment, the example in which the
interlayer insulating layers are laminated with two layers is
illustrated. In the case that the number of laminated layers is
increased, similarly an elastic modulus of the interlayer insulating
layer located just under the external connection terminals 34 may be set
lower than that of other interlayer insulating layer.

[0116] All examples and conditional language recited herein are intended
for pedagogical purpose to aid the reader in understanding the invention
and the concepts contributed by the inventor to furthering the art, and
are to be construed as being without limitation to such specifically
recited examples and conditions, nor does the organization of such
examples in the specification relates to a showing of the superiority and
interiority of the invention. Although the embodiments of the present
invention have been described in detail, it should be understood that the
various changes, substitutions, and alterations could be made hereto
without departing from the spirit and scope of the invention.